Changing the Clinical Paradigm of Hydroxyurea Treatment for Sickle Cell Anemia Through Precision Medicine

The feasibility of pharmacokinetic-based dosing of hydroxyurea for children with sickle cell anaemia in Uganda: Baseline results of the alternative dosing and prevention of transfusions trial

Pharmacokinetic (PK)-guided dosing of hydroxyurea for children with sickle cell anaemia (SCA) could optimize dosing and improve outcomes, but its feasibility has not been demonstrated in low-resource settings where the majority of affected children live. Alternative Dosing And Prevention of Transfusions (ADAPT) is a prospective trial evaluating blood transfusions and the feasibility of determining PK-guided, hydroxyurea maximum tolerated doses (MTD) for children with SCA in Uganda, using portable high-performance liquid chromatography (HPLC) and a novel PK software programme (HdxSim). ADAPT enrolled 106 participants, and 100% completed PK testing. PK-guided doses were generated for 78%, of which 38% were within the protocol-defined range. Accurately, measuring serum hydroxyurea concentrations via HPLC and the potential for hydroxyurea degradation impacted the feasibility. Ensuring that people with SCA globally have access to hydroxyurea is imperative, and improving treatment strategies requires ongoing innovation including PK-guided dosing. ADAPT is registered at ClinicalTrials.gov (NCT05662098).

The feasibility of pharmacokinetic-based dosing of hydroxyurea for children with sickle cell anaemia in Uganda: Baseline results of the alternative dosing and prevention of transfusions trial

Pharmacokinetic (PK)-guided dosing of hydroxyurea for children with sickle cell anaemia (SCA) could optimize dosing and improve outcomes, but its feasibility has not been demonstrated in low-resource settings where the majority of affected children live. Alternative Dosing And Prevention of Transfusions (ADAPT) is a prospective trial evaluating blood transfusions and the feasibility of determining PK-guided, hydroxyurea maximum tolerated doses (MTD) for children with SCA in Uganda, using portable high-performance liquid chromatography (HPLC) and a novel PK software programme (HdxSim). ADAPT enrolled 106 participants, and 100% completed PK testing. PK-guided doses were generated for 78%, of which 38% were within the protocol-defined range. Accurately, measuring serum hydroxyurea concentrations via HPLC and the potential for hydroxyurea degradation impacted the feasibility. Ensuring that people with SCA globally have access to hydroxyurea is imperative, and improving treatment strategies requires ongoing innovation including PK-guided dosing. ADAPT is registered at ClinicalTrials.gov (NCT05662098).

Optimization of hydroxyurea in sickle cell disease in Brazil

Despite sickle cell disease (SCD) being a well-recognized and highly prevalent condition identified early through neonatal screening programs, it represents a substantial public health challenge due to high morbidity and premature mortality rates. Hydroxyurea (HU) is the only available disease-modifying therapy for SCD approved in Brazil. Indeed, its underutilization highlights the need for improved therapeutic strategies to enhance adherence and management of SCD. Innovative formulations of HU might favor treatment adherence and precise dosing. Thus, we aimed to describe HU's pharmacological characteristics, clinical efficacy, and tolerability, including dose escalation. Recent interventional and observational studies revealed the efficacy and safety of an innovative formulation: dispersible scored tablets of 100 mg and 1000 mg, allowing easier dose adjustments and, consequently, more precise dosing. The 100 mg tablets scored can be cut into two parts of 50 mg, and the 1000 mg tablets can be cut into four parts of 250 mg. The fractionating dose is possible due to the formulation technology that allows the tablet to be cut with a uniform amount of drug in each part. This new formulation of HU, suitable for children, may influence the prognosis of SDC, regardless of associated symptoms.

Sickle cell disease in India: Not just a mild condition

Sickle cell disease (SCD) is a common and life-threatening global health problem, with more than 500 000 affected infants born annually. The burden of SCD in sub-Saharan Africa is well established, but the comparably high prevalence in India is not well recognized and many consider SCD in India to be less severe. In their paper, a national study in India demonstrated the significant impact of SCD for patients, families and the healthcare system, supporting a call to action to recognize and address SCD as a serious and common health condition in India. Commentary on: Seth et al. Burden of vaso-occlusive crisis, its management, and impact on quality of life of Indian sickle cell disease patients. Br J Haematol 2025; 206:296-309.

Hydroxyurea Pharmacokinetic Evaluation in Patients with Sickle Cell Disease

Background: Hydroxyurea (HU), also known as hydroxycarbamide, is an oral ribonucleotide reductase inhibitor. In 1999, the United States Food and Drug Administration (FDA) approved HU for the treatment of sickle cell disease (SCD). Since then, it has become the cornerstone in the management of SCD patients, helping to reduce vaso-occlusive crises, acute chest syndrome, the need for blood transfusions, hospitalizations and mortality. There is considerable variability among individuals in HU pharmacokinetic (Pk) parameters that can influence treatment efficacy and toxicity. The objective of this work is part of a clinical study aimed at investigating HU Pk and determining the optimal sampling time to estimate the Area Under the Curve (AUC) in SCD patients. Methods: HU plasma concentration in 80 patients at various time points (2, 4, 6, 24 h) following a 48-h drug washout was quantified using High-Pressure Liquid Chromatography (HPLC) coupled with an ultraviolet (UV) detection method previously described in the literature and adapted to new conditions with partial modifications. Results: The mean HU administered dose was 19.5 ± 5.1 mg/kg (range: 7.7-37.5 mg/kg). The median AUC quantified in plasma patients was 101.3 mg/L/h (Interquartile Range (IQR): 72.5-355.9) and it was not influenced by the weight-based dose. However, there was a strong positive correlation between AUC and Body Mass Index (BMI) as well as dose per Body Surface Area (BSA). Along with a three-point approach for AUC determination present in the literature, we show results obtained from a four-point sampling strategy, which is more useful and effective for better optimizing dose escalation to the maximum tolerated dose (MTD). Moreover, we observed that most patients achieved the maximum HU plasma concentration two hours after drug administration, regardless of age differences. Conclusions: HU treatment, which represents a milestone in the treatment of SCD due to its ability to reduce disease complications and improve patients' quality of life, requires careful monitoring to optimize the individual dose for saving potential side effects and/or adverse events.

Reviewing the impact of hydroxyurea on DNA methylation and its potential clinical implications in sickle cell disease

Hydroxyurea (HU) is the most common drug therapy for sickle cell disease (SCD). The clinical benefits of HU derive from its upregulation of fetal hemoglobin (HbF), which reduces aggregation of the mutated sickle hemoglobin protein (HbS) and reduces SCD symptoms and complications. However, some individuals do not respond to HU, or stop responding over time. Unfortunately, current understanding of the mechanism of action of HU is limited, hindering the ability of clinicians to identify those patients who will respond to HU and to optimize treatment for those receiving HU. Given that epigenetic modifications are essential to erythropoiesis and HbF expression, we hypothesize that some effects of HU may be mediated by epigenetic modifications, specifically DNA methylation. However, few studies have investigated this possibility and the effects of HU on DNA methylation remain relatively understudied. In this review, we discuss the evidence linking HU treatment to DNA methylation changes and associated gene expression changes, with an emphasis on studies that were performed in individuals with SCD. Overall, although HU can affect DNA methylation, research on these changes and their clinical effects remains limited. Further study is likely to contribute to our understanding of hematopoiesis and benefit patients suffering from SCD.

Hydroxyurea in the sickle cell disease modern era

INTRODUCTION

Sickle cell disease is an inherited disorder characterized by hemoglobin S polymerization leading to vaso-occlusion and hemolytic anemia. These result in a variety of pathological events, causing both acute and chronic complications. Millions around the world are affected by sickle cell disease with predominance in sub-Saharan Africa. Hydroxyurea was the first drug approved for use in sickle cell disease to reduce the occurrence of painful crises and blood transfusions in patients with frequent, moderate to severe painful crises.

AREAS COVERED

With the development of new therapeutics, the role of hydroxyurea is evolving. This narrative review aims to provide clinical data, safety information, and supplementary evidence for the role of hydroxyurea in the current era of sickle cell disease. A comprehensive literature search of databases, including PubMed and Cochrane Library, was conducted from 1963 to 2024.

EXPERT OPINION

Even though new medications have been approved for sickle cell disease, hydroxyurea remains the gold standard. Hydroxyurea is not only a disease modifier but it has additional clinical benefits, it is affordable, and its longevity has prompted expanded research in areas such as underutilization and pharmacogenomics. As the treatment landscape evolves, hydroxyurea's long-standing record of efficacy and safety continues to support its role as a key agent in disease management.

Rationale, Development, and Validation of HdxSim, a Clinical Decision Support Tool for Model-Informed Precision Dosing of Hydroxyurea for Children with Sickle Cell Anemia

Hydroxyurea treatment for children with sickle cell anemia (SCA) is effective and life-saving. Stepwise escalation to maximum tolerated dose (MTD) provides optimal benefits, but is logistically challenging and time-consuming, especially in low-income countries where most people with SCA live. Model-informed precision dosing (MIPD) of hydroxyurea expedites MTD determination and improves outcomes compared with trial-and-error dose adjustments. HdxSim, a user-friendly, online, clinical decision support tool was developed to facilitate hydroxyurea MIPD and evaluated using real-world pharmacokinetic (PK) data. First-dose hydroxyurea PK profiles were analyzed from two clinical trial datasets (Hydroxyurea Study of Long-Term Effects (HUSTLE), NCT00305175 and Therapeutic Response Evaluation and Adherence Trial (TREAT), NCT02286154). Areas under the concentration-time curve (AUC) estimated by HdxSim were compared with those determined using traditional trapezoidal methodology and PK software (MWPharm-DOS). The doses predicted by HdxSim and MWPharm-DOS were compared with the observed clinical MTD. For HUSTLE participants, HdxSim accurately estimated hydroxyurea AUC compared with the trapezoidal method, with < 20% variance. The average (mean ± SD) AUC for TREAT participants estimated with HdxSim (68.6 ± 18.0 mg*hour/L) was lower than MWPharm-DOS (78.6 ± 20.7 mg*hour/L, P = 0.012), but the average recommended doses were not different (425 vs. 423 mg/day, P = 0.97). Moreover, HdxSim was non-inferior to MWPharm-DOS at predicting clinical MTD (absolute difference 3.9 ± 5.8 vs. 4.9 ± 8.2 mg/kg/day, P = 0.19). HdxSim accurately estimates hydroxyurea exposure and is noninferior to traditional PK approaches at predicting the clinical hydroxyurea MTD. Hydroxyurea dosing based on target exposure leads to improved outcomes in children with SCA, and has the potential to make PK-guided hydroxyurea dosing more accessible to this neglected population globally.

Safety, tolerability, pharmacokinetics and pharmacodynamics of milvexian with aspirin and/or clopidogrel in healthy participants

Milvexian, an oral activated Factor XI (FXIa) inhibitor, is in clinical studies where it may be combined with antiplatelet agents, including aspirin and/or clopidogrel, to prevent thromboembolic diseases. This phase I trial assessed safety, pharmacokinetics, and pharmacodynamics of milvexian coadministration with aspirin and/or clopidogrel in healthy participants through 3 drug-drug interaction studies using a 3-period, 3-treatment, crossover design. A total of 113 participants were randomized to receive milvexian (200 mg; twice daily for 5 days) or matched placebo coadministered with once-daily aspirin (325 mg for 5 days) and/or clopidogrel (Day 1: 300 mg; Days 2-5: 75 mg). Milvexian was safe and well tolerated, with and without aspirin and/or clopidogrel. Eight mild bleeding adverse events (AEs) were reported in 5 of 113 participants across various treatment arms. Peak and total exposures of milvexian were similar with or without clopidogrel and/or aspirin. Exposure-dependent prolongation of activated partial thromboplastin time and reduction of FXI clotting activity by milvexian were similar with coadministration of aspirin and/or clopidogrel. Milvexian, with or without coadministration of aspirin and/or clopidogrel, did not affect bleeding time or platelet aggregation. Administration of milvexian alone or with aspirin and/or clopidogrel was safe and well tolerated without increased incidence of AEs, including bleeding. Pharmacokinetic and pharmacodynamic effects of milvexian, including bleeding time, were similar with or without aspirin and/or clopidogrel.ClinicalTrials.gov Identifier: NCT03698513.

Sickle Cell Disease in Brazil: Current Management

Sickle cell disease (SCD) comprises inherited red blood cell disorders due to a mutation in the β-globin gene (c20A > T, pGlu6Val) and is characterized by the presence of abnormal hemoglobin, hemoglobin S, hemolysis, and vaso-occlusion. This mutation, either in a homozygous configuration or in compound states with other β-globin mutations, leads to polymerization of hemoglobin S in deoxygenated conditions, causing modifications in red blood cell shape, particularly sickling. Vaso-occlusive crisis (VOC) is the hallmark of the disease, but other severe complications may arise from repeated bouts of VOCs. SCD is considered a global health problem, and its incidence has increased in some areas of the world, particularly the Americas and Africa. Management of the disease varies according to the region of the world, mainly due to local resources and socioeconomic status. This review aimed to describe more recent data on SCD regarding available treatment options, especially in Brazil. New treatment options are expected to be available to all patients, particularly crizanlizumab, which is already approved in the country.

Sickle Cell Disease: Current Drug Treatments and Functional Foods with Therapeutic Potential

Sickle cell anemia (SCA), the most common form of sickle cell disease (SCD), is a genetic blood disorder. Red blood cells break down prematurely, causing anemia and often blocking blood vessels, leading to chronic pain, organ damage, and increased infection risk. SCD arises from a single-nucleotide mutation in the β-globin gene, substituting glutamic acid with valine in the β-globin chain. This review examines treatments evaluated through randomized controlled trials for managing SCD, analyzes the potential of functional foods (dietary components with health benefits) as a complementary strategy, and explores the use of bioactive compounds as functional food ingredients. While randomized trials show promise for certain drugs, functional foods enriched with bioactive compounds also hold therapeutic potential. Further research is needed to confirm clinical efficacy, optimal dosages, and specific effects of these compounds on SCD, potentially offering a cost-effective and accessible approach to managing the disease.

Inherited disorders of hemoglobin: A review of old and new diagnostic methods

The genetic regulation of hemoglobin is complex and there are a number of genetic abnormalities that result in clinically important hemoglobin disorders. Here, we review the molecular pathophysiology of hemoglobin disorders and review both old and new methods of diagnosing these disorders. Timely diagnosis of hemoglobinopathies in infants is essential to coordinate optimal life-saving interventions, and accurate identification of carriers of deleterious mutations allows for genetic counseling and informed family planning. The initial laboratory workup of inherited disorders of hemoglobin should include a complete blood count (CBC) and peripheral blood smear, followed by carefully selected tests based on clinical suspicion and available methodology. We discuss the utility and limitations of the various methodologies to fractionate hemoglobin, including cellulose acetate and citrate agar hemoglobin electrophoresis, isoelectric focusing, high-resolution high-performance liquid chromatography, and capillary zone electrophoresis. Recognizing that most of the global burden of hemoglobin disorders exists in low- and middle-income countries, we review the increasingly available array of point-of-care-tests (POCT), which have an increasingly important role in expanding early diagnosis programs to address the global burden of sickle cell disease, including Sickle SCAN, HemoTypeSC, Gazelle Hb Variant, and Smart LifeLC. A comprehensive understanding of the molecular pathophysiology of hemoglobin and the globin genes, as well as a clear understanding of the utility and limitations of currently available diagnostic tests, is essential in reducing global disease burden.

A New Artificial Intelligence Approach Using Extreme Learning Machine as the Potentially Effective Model to Predict and Analyze the Diagnosis of Anemia

The procedure to diagnose anemia is time-consuming and resource-intensive due to the existence of a multitude of symptoms that can be felt physically or seen visually. Anemia also has several forms, which can be distinguished based on several characteristics. It is possible to diagnose anemia through a quick, affordable, and easily accessible laboratory test known as the complete blood count (CBC), but the method cannot directly identify different kinds of anemia. Therefore, further tests are required to establish a gold standard for the type of anemia in a patient. These tests are uncommon in settings that offer healthcare on a smaller scale because they require expensive equipment. Moreover, it is also difficult to discern between beta thalassemia trait (BTT), iron deficiency anemia (IDA), hemoglobin E (HbE), and combination anemias despite the presence of multiple red blood cell (RBC) formulas and indices with differing optimal cutoff values. This is due to the existence of several varieties of anemia in individuals, making it difficult to distinguish between BTT, IDA, HbE, and combinations. Therefore, a more precise and automated prediction model is proposed to distinguish these four types to accelerate the identification process for doctors. Historical data were retrieved from the Laboratory of the Department of Clinical Pathology and Laboratory Medicine, Faculty of Medicine, Public Health, and Nursing, Universitas Gadjah Mada, Yogyakarta, Indonesia for this purpose. Furthermore, the model was developed using the algorithm for the extreme learning machine (ELM). This was followed by the measurement of the performance using the confusion matrix and 190 data representing the four classes, and the results showed 99.21% accuracy, 98.44% sensitivity, 99.30% precision, and an F1 score of 98.84%.

Pharmacological Induction of Fetal Hemoglobin in β-Thalassemia and Sickle Cell Disease: An Updated Perspective

A significant amount of attention has recently been devoted to the mechanisms involved in hemoglobin (Hb) switching, as it has previously been established that the induction of fetal hemoglobin (HbF) production in significant amounts can reduce the severity of the clinical course in diseases such as β-thalassemia and sickle cell disease (SCD). While the induction of HbF using lentiviral and genome-editing strategies has been made possible, they present limitations. Meanwhile, progress in the use of pharmacologic agents for HbF induction and the identification of novel HbF-inducing strategies has been made possible as a result of a better understanding of γ-globin regulation. In this review, we will provide an update on all current pharmacological inducer agents of HbF in β-thalassemia and SCD in addition to the ongoing research into other novel, and potentially therapeutic, HbF-inducing agents.

Acute chest syndrome of sickle cell disease: genetics, risk factors, prognosis and management

IntroductionSickle cell disease, one of the world's most prevalent Mendelian disorders, is a chronic hemolytic anemia punctuated by acute vasoocclusive events. Both hemolysis and vasoocclusion lead to irreversible organ damage and failure. Among the many sub-phenotypes of sickle cell disease is the acute chest syndrome (ACS) characterized by combinations of chest pain, cough, dyspnea, fever, abnormal lung exam, leukocytosis, hypoxia, and new radiographic opacities. ACS is a major cause of morbidity and mortality.Area coveredWe briefly review the diagnosis, epidemiology, etiology, and current treatments for ACS and focus on understanding and estimating the risks for developing this complication, how prognosis and outcomes might be improved and the genetic elements that might impact the risk of ACS.Expert opinionThe clinical heterogeneity of ACS has hindered our understanding of risk stratification. Lacking controlled clinical trials most treatment is based on expert opinion. Fetal hemoglobin levels and coexistent α thalassemia affect the incidence of ACS; other genetic associations are tenuous. Transfusions, whose use not innocuous, should be targeted to the severity and likelihood of ACS progression. Stable, non-hypoxic patients with favorable hematologic and radiographic findings usually do not need transfusion; severe progressive ACS is best managed with exchange transfusion.

MicroRNAs and JAK/STAT3 signaling: A new promising therapeutic axis in blood cancers

Blood disorders include a wide spectrum of blood-associated malignancies resulting from inherited or acquired defects. The ineffectiveness of existing therapies against blood disorders arises from different reasons, one of which is drug resistance, so different types of leukemia may show different responses to treatment. Leukemia occurs for a variety of genetic and acquired reasons, leading to uncontrolled proliferation in one or more cell lines. Regarding the genetic defects, oncogene signal transducer and activator of transcription (STAT) family transcription factor, especially STAT3, play an essential role in hematological disorders onset and progress upon mutations, dysfunction, or hyperactivity. Besides, microRNAs, as biological molecules, has been shown to play a dual role in either tumorigenesis and tumor suppression in various cancers. Besides, a strong association between STAT3 and miRNA has been reported. For example, miRNAs can regulate STAT3 via targeting its upstream mediators such as IL6, IL9, and JAKs or directly binding to the STAT3 gene. On the other hand, STAT3 can regulate miRNAs. In this review study, we aimed to determine the role of either microRNAs and STAT3 along with their effect on one another's activity and function in hematological malignancies.

Early initiation of hydroxyurea (hydroxycarbamide) using individualised, pharmacokinetics-guided dosing can produce sustained and nearly pancellular expression of fetal haemoglobin in children with sickle cell anaemia

Hydroxyurea (hydroxycarbamide) is an effective treatment for sickle cell anaemia (SCA), but clinical responses depend primarily upon the degree of fetal haemoglobin (HbF) induction and the heterogeneity of HbF expression across erythrocytes. The number and characteristics of HbF-containing cells (F-cells) are not assessed by traditional HbF measurements. Conventional hydroxyurea dosing (e.g. fixed doses or low starting doses with stepwise escalation) produces a moderate heterocellular HbF induction, but haemolysis and clinical complications continue. Robust, pancellular HbF induction is needed to minimise or fully inhibit polymerisation of sickle haemoglobin. We treated children with hydroxyurea using an individualised, pharmacokinetics-guided regimen starting at predicted maximum tolerated dose (MTD). We observed sustained HbF induction (mean >30%) for up to 6 years, which was not dependent on genetic determinants of HbF expression. Nearly 70% of patients had ≥80% F-cells (near-pancellular), and almost half had ≥90% F-cells (pancellular). The mean HbF/F-cell content was ~12 pg. Earlier age of initiation and better medication adherence were associated with high F-cell responses. In summary, early initiation of hydroxyurea using pharmacokinetics-guided starting doses at predicted MTD can achieve sustained near-pancellular or pancellular HbF expression and should be considered an achievable goal for children with SCA treated with hydroxyurea at optimal doses. Clinical trial registration number: NCT02286154 (clinicaltrials.gov).